“…Magnetic nanoparticles are of great interest to scientists and technologists due to their favorable magnetic and electrical properties, especially iron-oxide-based nanoparticles (MFe 2 O 4 , M = Fe, Mn, Co, Zn, or Ni, etc.). Although MFe 2 O 4 nanoparticles have exhibited excellent characteristics in the biomedical field, their safe application in the human body is a major problem owing to the heavy metal elements presented in MFe 2 O 4 [1], which also limits their applications in the biomedical field. So, as one of the typical nanomaterials, spinel iron oxide nanoparticles without heavy metal elements have been widely applied in many aspects of the biomedicine field due to their good biocompatibility and no toxicity or low toxicity in organisms [2,3], such as magnetic resonance imaging (MRI) [4], clinical diagnosis and the treatment of diseases [5,6], magnetic carriers for drug targeting [7], catalysis [8][9][10][11][12], immune assays [13], targeting photodynamic therapy [14][15][16], cell separation [17], DNA extraction [18], and so on.…”